Arturo Molina Ocampo

Background: Magnesium-based alloys have emerged as promising biodegradable materials for temporary biomedical implants due to their biocompatibility, low density, and elastic modulus similar to natural bone. However, their rapid degradation in physiological environments limits their clinical application, making surface modification strategies necessary to improve corrosion resistance and mechanical performance. Objective: The aim of this study was to evaluate the effect of ionic nitriding on the microstructure, corrosion resistance, mechanical properties, and cytocompatibility of Mg–Zn–Ca–Mn biodegradable alloys. Methods: Mg–Zn–Ca–Mn quaternary alloys were synthesized by powder metallurgy and subsequently surface modified by ionic nitriding. The microstructure and phase composition were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Corrosion behavior was evaluated through electrochemical tests in Hank's solution, while mechanical properties were assessed using Vickers microhardness measurements. Cytocompatibility was analyzed by indirect cytotoxicity tests using fibroblast and keratinocyte cells. Results: The nitrided alloys exhibited improved corrosion resistance, evidenced by lower corrosion current densities and more noble corrosion potentials compared with pure magnesium. In addition, ionic nitriding increased the Vickers microhardness by approximately 42–48%. Cytotoxicity assays showed that the Mg64–Zn30–Ca5–Mn1 alloy and its nitrided counterpart-maintained cell viability above 70%, indicating acceptable cytocompatibility. Conclusion: Ionic nitriding is an effective surface modification technique to enhance the corrosion resistance, mechanical properties, and biological performance of Mg–Zn–Ca–Mn biodegradable alloys, demonstrating their potential for use as temporary biomedical implant materials.

Polyhydroxybutyrate (PHB) is considered a coating material capable of limiting the corrosion of biodegradable metallic implants due to its biocompatibility and ability to form a physical barrier. In this study, PHB was deposited on commercial AZ91D magnesium alloy using the spin coating technique. To improve adhesion at the polymer–substrate interface, the magnesium substrates were subjected to atmospheric pressure plasma treatment for different exposure times (5, 10, or 15 min) before coating. The optimal treatment time of 5 min significantly increased substrate wettability and surface free energy, facilitating stronger PHB adhesion. In addition, the PHB coatings were subjected to atmospheric pressure plasma treatment for 5, 10, or 15 s to evaluate potential surface modifications. Corrosion behavior under simulated physiological conditions was assessed via potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in HANK’s solution at 37 °C. Pull-off tests were used to evaluate the adhesion strength between the coating and the substrate under each treatment condition. The results showed a significant decrease in the corrosion rate (V_corr), from 4.083 mm/year for bare Mg-AZ91D to 0.001 mm/year when both the substrate and the polymer received plasma treatment. This indicates that the treatment modifies surfaces and improves interfacial bonding, enhancing polymer–metal interaction and producing durable, biocompatible coatings for medical implants.

Metallic glasses (MGs) are a type of multicomponent non-crystalline metallic alloys obtained by rapid cooling, which possess several physical, mechanical, and chemical advantages against their crystalline counterparts. In this work, an Fe-based MG is explored as a hydrogen storage material, especially, due to the evidence in previous studies about the capability of some amorphous metals to store hydrogen. The evaluation of an Fe-based MG as a novel negative electrode material for nickel/metal hydride (Ni-MH) batteries was carried out through cyclic voltammetry and galvanostatic charge–discharge tests. A conventional LaNi5 electrode was also evaluated for comparative purposes. The electrochemical results obtained by cyclic voltammetry showed the formation of three peaks, which are associated with the formation of Fe oxides/oxyhydroxides and hydroxides. Cycling charge/discharge tests revealed activation of the MG electrode. The highest discharge capacity value was 173.88 mAh/g, but a decay in its capacity was observed after 25 cycles, contrary to the LaNi5, which presents an increment of the discharge capacity for all the current density values evaluated, reached its value maximum at 183 mAh/g. Characterization analyses performed by X-ray diffraction, Scanning Electron Microscopy and Raman Spectroscopy revealed the presence of corrosion products and porosity on the surface of the Fe-based MG electrodes. Overall, the Fe-based MG composition is potentially able to work as a negative electrode material, but degradation and little information about storage mechanisms means that it requires further investigation.

In the present work, the powder metallurgy (PM) technique was used to synthesize biocompatible alloys Mg95–Zn5, Mg90–Zn10, and Mg85–Zn15 (wt %) under an argon atmosphere that employed stainless-steel vessels and spheres with a milling treatment of 360 rpm during 15 h. The obtained powder was consolidated through a sintering process for subsequent ion nitriding treatment to increase its corrosion resistance and hardness. The synthesized alloys analyzed by Scanning electron microscopy (SEM) images showed a reduction in particle size with increasing grinding time. The X-ray diffraction (XRD) results showed the formation of a MgZn intermetallic phase and, furthermore, that no impurities were found during the grinding process. The surface-modified Mg–Zn alloys showed some improvement in terms of corrosion (Ecorr 26% and Icorr 13%) and microhardness (HV 40%) compared to Mg. Cytotoxicity evaluation was conducted via an MTT ((3-(4,5-DIMETHYLTHIAZOL-2-YL)-2,5-DIPHENYLTETRAZOLIUM BROMIDE)) assay, which revealed that the Mg–Zn alloys and nitrided samples did not exhibit cytotoxicity towards fibroblast cells after 96 h.

The biocompatibility and biodegradability of magnesium (Mg), along with its lightness, make magnesium-based materials promising for use in the biomedical industry. In this work, ternary Mg–Zn–Ca alloys were manufactured for biomedical applications using mechanical alloying (MA). The objective of this work was to study the effect of milling time on the produced ternary alloys Mg65–Zn30–Ca5 and Mg70–Zn25–Ca5 (percentages by weight), the degradation of the alloys in synthetic human fluids, and their generated cytotoxicity. The Mg-based alloys were synthesized in a planetary ball mill under an argon atmosphere using stainless-steel containers and balls with a milling regimen of 400 rpm for 2, 5, 10, 15, and 20 h. The powders obtained after MA were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), which verified that ternary Mg–Zn–Ca alloys can be obtained using MA. The XRD refinement analysis of the samples showed the presence of a MgZn intermetallic phase. Electrochemical tests showed that the corrosion resistance and corrosion current density of Mg65–Zn30–Ca5 and Mg70–Zn25–Ca5 alloys improved compared to those of pure Mg. Cytotoxicity testing was conducted using the Sulforhodamine B (SRB) assay, which revealed that the alloys did not exhibit cytotoxicity toward human fibroblast cells. Mg65–Zn30–Ca5 and Mg70–Zn25–Ca5 alloys show good potential to be used in biomedical applications.

In this study, a nano-composite material of a nanostructured Al-based matrix reinforced with Fe40Al intermetallic particles was produced by ball milling. During the non-equilibria processing, the powder mixtures with the compositions of Al-XFe40Al (X = 5, 10, and 15 vol. %) were mechanically milled under a low energy regime. The processed Al-XFe40Al powder mixtures were subjected to uniaxial pressing at room temperature. Afterward, the specimens were subjected to a sintering process under an inert atmosphere. In this thermal treatment, the specimens were annealed at 500 °C for 2 h. The sintering process was performed under an argon atmosphere. The crystallite size of the Al decreased as the milling time advanced. This behavior was observed in the three specimens. During the ball milling stage, the powder mixtures composed of Al-XFe40Al did not experience a mechanochemical reaction that could lead to the generation of secondary phases. The crystallite size of the Al displayed a predominant tendency to decrease during the ball milling process. The microstructure of the consolidated specimens indicated a uniform dispersion of the intermetallic reinforcement phases in the Al matrix. Moreover, according to the Vickers microhardness tests, the hardness varied linearly with the increase in the concentration of the Fe40Al intermetallic phase present in the composite material. The presented graphs indicate that the hardness increased almost linearly with the increasing dislocation density and with the reduction in grain sizes (both occurring during the non-equilibria processing). The microstructural and mechanical properties reported in this paper provide the aluminum matrix composite materials with the ideal conditions to be considered candidates for applications in the automotive and aeronautical industries.

Digital image processing is a useful tool that improves pictorial information for human interpretation and is mainly used for storage, transmission, and representation of different data. In this chapter, we want to introduce an optical technique which couples physical analysis with image processing for a measurement system. Optical methods were used to obtain the stress-strain relation by different invasive and noninvasive methods. This chapter talks about a novel noninvasive methodology to measure stress-strain evolution; this technique is based upon a single laser beam reflected on the cross section of ductile materials (steel and aluminum) while they are under a compression load. The way we measure one laser beam is by using the Gaussian beam propagation equations; we propose that the reflection area of the laser is going to change as the material surface area is compressed and we analyze these differences by using digital image processing. With this technique we are able to construct a stress-strain diagram.